The present invention relates to devices designed for use with lighting systems, and particularly to a control system for a combination timer and motion detector for use with lighting which turns off the lighting after a certain time period after dark, and turns the lighting back on during the dark period upon detection of motion.
There are many situations where lighting needs to be controlled in an automatic manner. Timers have been used to turn off lighting at a precise time of day when a building is unoccupied to give the impression that people are present within the building. Such impressions lessen the likelihood that the building will be burglarized or vandalized. A major drawback to the use of a timer is the precision with which it operates. If a potential burglar or vandal notices that the lights are shut down at a precise time of day over a period of days, he might conclude that the building is unoccupied.
Many commonly obtainable timers are motor driven and based on a 24 hour period. The current required for the motor drive usually militates against the use of battery backup in small systems. As a result, a loss of power will cause such a system to shift its timing forward such that the lighting is turned on later and turned off later. The change in timing wastes electricity to the extent that the lighting is on during the daytime, and risks the impression of non-occupancy in the time period between the time when the lights should have been turned on and when they actually have been turned on.
Other systems for lighting control include the dusk to dawn control systems. These systems are configured to turn lights on and off solely based upon the amount of sunlight present. These systems are primarily designed to keep the perimeter of a building illuminated constantly, and are not intended to give an impression of building occupancy.
Controlling a lighting system based on the amount of sunlight present has disadvantages based upon energy usage. Since the illuminated area will remain illuminated all night, the energy consumption is greater than that which would be required for an illumination period lasting from one third to one half of the night time. Further, it may be easier to notice an illumination cycle which occurs solely at the dawn and dusk hours and which is therefore indicative of a dusk to dawn control system.
A further method of control for a light system is the use of the motion detector. A motion detector may use a variety of methods of detecting movement including infrared, sound, or visible optics. A simple motion detector may be activated to switch on a light upon the detection of motion. However, there may be significant amounts of normal activity during the early evening hours which would undesirably activate the lighting system which the motion detector is controlling.
In the case of a sonic detection system, cars or people may continue to move within the monitored area in the time period before illumination based upon movement is to occur. In the case of a light based detection system, car headlights from a high traffic level in the monitored area may cause the detection system to be repeatedly tripped in the early evening. Infrared based systems may repeatedly trip due to pedestrian traffic in the early evening. Such repeated tripping would reveal the presence of a motion detection system which could lead to its being disabled during the daylight hours. Ideally, a motion detection system should operate unexpectedly upon an intruder at a time when the intruder will most likely be in the monitored area improperly.
Another problem with controlled lighting systems is the effort required to override the timed, dusk to dawn, and motion detection controls. The user usually is forced to approach the timer box which may be remotely located from the light switch. The timer must be tripped, reset, or disabled, depending upon its configuration.
What is needed in lighting control technology is a method which eliminates several of the disadvantages in timer only, motion detection only, and dusk to dawn only lighting control. The presence of motion control should be masked during the early evening when continued activity is present. The timed turning on and off of the light should not occur at the same time each day. The motion control aspect of lighting control should be totally disabled in the daytime both to mask the presence of motion detection and to save energy in not lighting the area during daylight.